Charging '101' for Yamaha Road Stars

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Written by Mr Tidy   
Thursday, 10 June 2004

Reprinted by Permission from Mr Tidy's Tech Tips

Charging problems can drive you up the wall.  Adding to this is the fact that there seems to be no easy way for us simpleton's to verify that the Regulator/Recitifier is good or faulty. This primer goes along that line, as does the Yamaha Service Manual.
 

The Service Manual leaves some to be desired and I hope I've explained it a bit further so you can successfully troubleshoot your charging circuit.
The main idea is to verify that your stator is either good or bad and that your circuit wiring is good or bad. If after running this troubleshooting procedure and no faults are found, it leaves only one logical option, a bad Regulator/Rectifier.
 

The charge circuit is quite simple.  We first have to absolutely qualify or
disqualify the stator and associated wiring, we then can reasonably determine that the R/R is either good or faulty.

1.   Start off with a fully charged battery. Set your multimeter on the 50V DC range and hook to battery, You should read 12.6VDC to 12.8VDC 

2.    With meter still attached, Start your engine and read voltage. You should be reading between 13.5VDC and 14VDC If this is true then your charge system is OK. If your charge rate is higher than 14VDC you have a possible bad regulator and your battery is in danger of being damaged from overcharging.  If voltage is lower than 13.5VDC then go to step #

3.    Disconnect the 5 pin connector, 'A', at the top of the Regulator / Rectifier.
       Check for corrosion, if a problem is present, then clean all connections and
       re-try step #2.
       If no problem is seen then proceed to step #4.


Click on image for larger view

Remove vinyl cover aSwivelnd depress catch and
pull upward on connector.

B =  Black ground,  R = Red Battery Pos +
W = White wires from Stator windings

4.    Set your multimeter to the Ohm's scale X 1.  Open up the Left-hand side cover, in front of the battery,  a cable clamp with several bundles of wire and connectors are present, one connector has 3 white wires going in and out of the opposing connector.  This is connector 'B' in the diagram below.

Hold one test lead to any stator lead.
Hold other test lead to any other stator lead. Note reading. 
Repeat at all pairs of test leads 
Equal readings should be obtained at each pair of stator leads.
Your readings should be between .45 ~ .55 ohms on all three pin sets of the plug.
If readings are + or - a bit , do not automatically decide the stator is bad, temperature,
materials, and tools can give a fluxuation of readings. We are looking for a reading close 
and equal to the .45 ~.55 ohms specified. A reading of .6 is not unusual.
If not, then stator has open or has shorted windings or open wire from connector to stator windings, repair wire or replace stator.
If readings are Ok then proceed to Step #5.


Click on image for larger view

    
    

5.    If all 3 readings are within specified range then insert meter probe into each pin of
       connector to the motorcycle frame (ground). 
       If any reading is less than infinity, then the stator is grounded. 
       Replace Stator.
       If readings are infinite then go to step #6

   
   

   
   

6.    If the stator checks good then,
       Set multimeter to 50VCD range and insert probes into the Red and Black wired pins
       on the R/R connector (connector A). 
   

               click to enlarge
   

       You should read battery voltage.  If not, Main Fuse is bad or an open wire is present.
      Replace Main Fuse or look for open wire.
       If battery voltage is present then Main Fuse and wiring are OK.
       Goto Step #7.
   
   

7.    Check wiring continuity between connector 'A' and connector 'B', with multimeter
       set on the ohm's scale at X 1.  The readings are taken from the "white" wires.

                   This the larger "B" connector with spade pins.
                                                    its wires run directly to the "A" connector. 

       If a reading of infinity is present in any wire then repair open wire. 
       If all wires show continuity then proceed to Step #8.
   

8.    If the stator has checked Ok, 
       battery voltage is present on Red and Black pins of (A),
       and all wiring is intact. 
       Goto Step #9
   

9.    Set multimeter to 200VAC scale, 
       Start your engine leave at idle
       Hold one test lead to any stator lead on connector 'B'. 
       Hold other test lead to any other stator lead. Note reading. 
       At idle you should read @ 30VAC
       Repeat on all pairs of leads. 
       Equal readings should be obtained at each pair of stator leads.
       Rev engine to @ 1500 RPM's and repeat voltage readings,
       Equal readings of @ 80VAC should be obtained at each pair of stator leads.

      If reading are all equal and in range then reconnect the (B) connector in front of battery
       and re-check the readings at the "W" terminals on the "A" connector. The readings
       should be the same as at the previous connector. If in range and equal on each pair.
       We have verified that your Stator windings and associated wiring are intact, 
       Regulator / Rectifier is bad, Replace

      If readings are not in range and equal for each pair of pins, then stator has open wire,
       shorted, open winding, connections are breaking down, or open wire, 
       retrace steps #3 thru #9 to verify problem.




Questions should be asked in our forum (Use discuss link below). The forum is very active and you stand a good chance of getting your questions answered there. If you would like to leave feedback for the author, or have additional information you think will benefit others, please use the comment section at the bottom of this page.

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DISCLAIMER: This information and procedure is provided as a courtesy and is for informational purposes only.  Neither the publishers nor the authors accept any responsibility for the accuracy, applicability, or suitability of this procedure.  You assume all risks associated with the use of this information.  NEITHER THE PUBLISHERs NOR THE AUTHORs SHALL IN ANY EVENT BE LIABLE FOR ANY DIRECT, INDIRECT, PUNITIVE, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, OF ANY NATURE ARISING OUT OF OR IN ANY WAY CONNECTED WITH THE USE OR MISUSE OF THIS INFORMATION OR LACK OF INFORMATION.  Any type of modification or service work on your motorcycle should always be performed by a professional mechanic. If performed incorrectly, this procedure may endanger the safety of you and others on your motorcycle and possibly invalidate your manufacturer’s warranty.


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  Comments (7)
Ohms Question
Written by Jfogle01, on 04-11-2016 09:34
Hello. I wanted to know your opinion on this....when checking the ohms across the three connections, I'm getting 0.9 on all three. Would you consider that too high? I've already replaced the battery and the reg/rec, for an 06 since I plan to finish off with the stator upgrade, but want to know if I have some time before having to do the stator. All thoughts would be great, thanks!
Just a double check!
Written by Jfogle01, on 04-05-2015 10:49
Excellent write up! I just have simple question.....when checking my voltage, I get 12.4 with the key off, 13.5@low idle and 14.6@half choked idle. I'm pretty comfortable with this but just want to make sure that it actually IS ok. Thanks for the help!!! 
 
HAPPY EASTER ROADSTAR CLINIC!!!
Can someone help?
Written by pauldeli, on 04-05-2009 07:17
Hey Help! 
2004 Roadstarm- went through the charging 101 and all appears to check out. I have checked the voltage a few times before doing the testing as reccommended and found the voltage once over 14 then another time less than 14 so went through the system and changed the rectifier and another new battery as the other over charged, I think. Anyway still showing 14.2 volts when running at a idle, so I disconnected my new battery and said ********** 
 
Any other things to check? I hate electrical problems. 
Also I have no extras hooked up, stock system. 
 
HELP!!!!!!
another angle on charging - basic - migh
Written by arty, on 12-04-2008 02:12
I had some problems a while back, bike would barely turn over - had to jump start and roll start from time to time. Then I adjusted my idle by about 1/8th turn - problem was gone. Seems these things rev so low that even at idle we need enough revs to pump power through the regulator. Thanks - great site.
RE: Charging 101
Written by Steef, on 02-08-2008 09:30
Greeting Floks, Been awhile since I've been on,,,, Did have to do a charging check to see if the Roadie was charging!!! Had the original battery go out on me and installed a new one back in October!!! Nothing but starting problems, Jumping the bike off the lawn tractor and finally broke down and bought a battery charger.... after a few weeks of that mess, I found I had a bad battery, got a replacement (Free of Charge) and performed the the printed check and found everything to be in working order... Great Info for all!!!! Thanks again!!! 
 
Regards 
 
Steef :grin
charging system
Written by rstarny, on 10-02-2007 18:24
i've done all the system checks and this is what i have, ohm readings on stator .8 on all pairs but all go to ground when tested.Bad stator right. then i start the bike meter on VAC get about 34VAC on all 3 stator leads and about 85 VAC @1500 rpm on all 3 so now i'm confused :? wiring checks good between reg and stator any help is great  
thanks  
Scott
Charging 101.
Written by bustedbiker, on 03-03-2007 16:57
Excellent article Mr Tidy :)  
 
However there are a few additional checks you can perform on the regulator/rectifier before you write it off. 
 
1. Using a meter on the 1x Ohms range (Some digital meters have a diode symbol use this range) 
2. Measure between all the white wire connections on the regulator they should read open. 
3. Reverse the meter connections and repeat step 2 
4. Measure between the each white wire and the positive pin on the regulator 
5. Reversing the polarity for each measurement. you should get a reading in one direction and open the other. 
repeat steps 4 and 5 between the white and black terminals. (This checks out the rectifier part of the regulator) 
6. Connect your battery between each white wire in turn and measure the voltage across the red and black terminals, you should read nearly battery voltage (Minus about .7 volts)  
7. Reverse the battery polarity and repeat step 6. 
 
The next steps test the regulator but you will need three 12 volt batteries and a 12 volt 3-6 Watt globe. 
 
8. Connect two of the batteries up in series so you get 24 volts. 
9. Connect the 12 volt globe in series with the 3rd Battery (this acts as a current limiter and indicator) 
 
10. Connect the 12 volt battery and test lamp between a white and the black terminal on the regulator observing the polarity (positive to the white). The lamp should not be lit. 
11. Momentarily (less than a second or you could damage the regulator)connect the 24 volt battery accross the red and black terminals ensuring red is positive and black negative. 
12. The lamp should light and remain lit until it is disconnected. 
13 Briefly disconnect the lamp to turn it off. 
14. Repeat steps 10 to 13 for the remaining white 3 wires. 
 
If the lamp does not operate as described above the regulator is faulty. 
 
Cheers 
BustedBiker.  
 
Keep the shiny side up.

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